FT-584 use trylock inside of the lock tree manager get_status function so that it is non-blocking

locktree/manager.cc

@@ -598,32 +598,32 @@ void locktree::manager::get_status(LTM_STATUS statp) {
     STATUS_VALUE(LTM_LONG_WAIT_ESCALATION_COUNT) = m_long_wait_escalation_count;
     STATUS_VALUE(LTM_LONG_WAIT_ESCALATION_TIME) = m_long_wait_escalation_time;    
 
-    mutex_lock();
-
     uint64_t lock_requests_pending = 0;
     uint64_t sto_num_eligible = 0;
     uint64_t sto_end_early_count = 0;
     tokutime_t sto_end_early_time = 0;
 
-    struct lt_counters lt_counters = m_lt_counters;
+    size_t num_locktrees = 0;
+    struct lt_counters lt_counters = {};
 
-    size_t num_locktrees = m_locktree_map.size();
+    if (toku_mutex_trylock(&m_mutex) == 0) {
+        lt_counters = m_lt_counters;
+        num_locktrees = m_locktree_map.size();
         for (size_t i = 0; i < num_locktrees; i++) {
             locktree *lt;
             int r = m_locktree_map.fetch(i, &lt);
             invariant_zero(r);
-
-        toku_mutex_lock(&lt->m_lock_request_info.mutex);
+            if (toku_mutex_trylock(&lt->m_lock_request_info.mutex) == 0) {
                 lock_requests_pending += lt->m_lock_request_info.pending_lock_requests.size();
                 add_lt_counters(&lt_counters, &lt->m_lock_request_info.counters);
                 toku_mutex_unlock(&lt->m_lock_request_info.mutex);
-
+            }
             sto_num_eligible += lt->sto_txnid_is_valid_unsafe() ? 1 : 0;
             sto_end_early_count += lt->m_sto_end_early_count;
             sto_end_early_time += lt->m_sto_end_early_time;
         }
-
         mutex_unlock();
+    }
 
     STATUS_VALUE(LTM_NUM_LOCKTREES) = num_locktrees;
     STATUS_VALUE(LTM_LOCK_REQUESTS_PENDING) = lock_requests_pending;

portability/toku_pthread.h

@@ -213,6 +213,21 @@ toku_mutex_lock(toku_mutex_t *mutex) {
 #endif
 }
 
+static inline int
+toku_mutex_trylock(toku_mutex_t *mutex) {
+    int r = pthread_mutex_trylock(&mutex->pmutex);
+#if TOKU_PTHREAD_DEBUG
+    if (r == 0) {
+        invariant(mutex->valid);
+        invariant(!mutex->locked);
+        invariant(mutex->owner == 0);
+        mutex->locked = true;
+        mutex->owner = pthread_self();
+    }
+#endif
+    return r;
+}
+
 static inline void
 toku_mutex_unlock(toku_mutex_t *mutex) {
 #if TOKU_PTHREAD_DEBUG